The present invention relates to cooling systems for endless track vehicles. Particularly, the present invention relates to snowmobiles having an improved cooling system. More particularly the present invention relates to a heat exchanger assembly utilized in snowmobile vehicles having liquid-cooled engines.
The invention is particularly applicable to self propelled snow vehicles more commonly referred to as snowmobiles and will be described with particular reference thereto; however, it will be appreciated by those skilled in the art that the invention has broader applications and may be advantageously employed in other types of vehicles requiring the use of small, fluid-cooled internal combustion engines.
Past snowmobiles have used-liquid cooling systems to cool their internal combustion engines. Snowmobiles with these liquid-cooled engines often have auxiliary radiators (also known as heat exchangers or coolers) spaced away from the engine itself. In some of these snowmobiles, the radiators are positioned within the drive tunnel, which is within the snowmobile chassis. The drive track, also disposed within the drive tunnel, carries and circulates snow within the drive tunnel as the track moves. The radiators are positioned adjacent the track so that some of the snow carried by the track will be thrown at the radiators to provide a heat exchange. The melting of snow requires a substantial amount of heat, which is removed from the coolant circulated in the radiators.
Aside from circulating snow within the tunnel, the drive track in typical snowmobiles will throw snow onto the snowmobile operator""s foot area. Since typical snowmobiles provide recessed footwells for a rider""s feet, the snow kicked up by the track and by movement of the machine tends to accumulate in the recesses of the footwells. The accumulated snow not only adds undesirable weight to the machine, but it may also cause the rider""s feet to slip from the snowmobile.
These heat exchangers (front, rear, left side, right side) and the rubber hoses that interconnect the heat exchangers form a coolant xe2x80x9ccircuitxe2x80x9d. For instance, a typical prior art series coolant circuit is shown schematically in FIG. 1. The circuit includes a right cooler 100, a rear cooler 102, a left cooler 104 and a front cooler 106. Each of the coolers are connected via flexible or formed hoses 108. The inlet side of the coolant circuit is connected to the engine 110 via a thermostat valve 112, as described below. The outlet of the coolant circuit is connected back to the engine 110 via a coolant pump 114. Often times, a coolant overflow reservoir 116 is inserted in the coolant circuit.
Typical engine thermostats 112 comprise temperature-actuated valves that open only when the engine temperature exceeds a threshold level (e.g., 120xc2x0 F.). When the engine temperature falls back below the threshold, the thermostat valve 112 closes. When the thermostat valve 112 is opened, the coolant is pumped via pump 114 through the circuit components generally in the following order: engine 110, right side cooler 100, rear cooler 102, left side cooler 104, front cooler 106, overflow reservoir 116, and back to pump 114. The flow of coolant through the coolers dissipates heat generated by the engine during its operation.
On conventional liquid cooled engines 110 having a thermostat valve 112, a second coolant outlet 118 is found (either as part of the thermostat or on the engine separate from the thermostat 112). As shown in FIG. 1, coolant from outlet 118 is routed back to the pump 114 directly (via hose 108 as shown in FIG. 1) or almost directly (by first passing through the overflow reservoir 116 which is connected to the pump 114).
Under this conventional configuration, at temperatures below the thermostat""s threshold, thermostat 112 is closed (cutting off fluid flow to all coolers) and outlet 118 remains open. Under these conditions (typically during initial engine warm-up), coolant is circulated out outlet 118 and directly back to the pump 114. Such direct or short circuit routing (bypassing all coolers) allows the engine to heat up to normal operating temperature as quickly as possible. Outlet 118 is used to direct the coolant back into engine 110 through pump 114 to achieve this objective. Then, once the engine reaches the thermostat""s threshold temperature, thermostat 112 opens to allow coolant to travel through the series coolant circuit 100, 102, 104, 106. If the water temp falls again below the threshold, thermostat 112 closes until the threshold is reached again.
In certain conventional cooling systems, a xe2x80x9cpopitxe2x80x9d style thermostat 112 is used. A popit thermostat closes outlet 118 under certain conditions. The popit style thermostat comprises a valve that has internally a flat disc that seals off outlet 118 and opens thermostat 112 when the temperature threshold is exceeded (allowing coolant to flow only out the thermostat 112 and to the cooling circuit. Conversely, the popit thermostat seals off thermostat 112 and opens outlet 118 at temperatures below the threshold (allowing coolant to flow only through outlet 118).
In either of these past designs, air is allowed to build up in the coolers and in the connecting hoses when coolant is not being pumped through them. When the past designs reached the temperature threshold and started pumping coolant, the air is eventually pumped out of the coolers and the hoses and into the overflow reservoir. Until the air is pumped out, though, the system does not provide maximum cooling. Air, of course, does not have the heat transfer capabilities of the engine coolant.
The invention provides a snowmobile with a liquid-cooled engine, first and second coolant circuits, and a pump. The engine has a cooling jacket that carries liquid that absorbs heat generated by the engine during operation. The first and second coolant circuits dissipate heat generated by the engine and each include at least one of a front cooler, a rear cooler, a left side cooler, and a right side cooler. The jacket is operatively connected with the coolers in the first and second cooling circuits. The jacket is connected between a respective inlet and outlet of each cooling circuit. The pump is used to circulate coolant through the cooling jacket and the cooling circuits. A thermostat valve is operatively connected to the second coolant circuit. The valve is biased to a closed position, blocking the pump""s circulation of coolant at a location in the second coolant circuit without blocking coolant circulation in the first coolant circuit. The valve opened when the engine temperature exceeds a predetermined threshold, thereby permitting coolant circulation in the second coolant circuit in order to increase the engine heat dissipated.
The outlets of the cooling circuits may share a common passage. In addition, the first coolant circuit may include the front cooler, the rear cooler, and the side coolers. The second coolant circuit may include the front cooler.
In one embodiment, the front cooler includes two inlets, one inlet for connection within each coolant circuit, and may have just one outlet, shared by each coolant circuit.
One embodiment of the invention takes advantage of the engine""s two outlets. Instead of routing the open outlet directly into the overflow reservoir, the present invention routes the open outlet into the first coolant circuit which is comprised of one or more of a left cooler, right cooler, rear cooler, and front cooler. Under this configuration, the first coolant circuit is always cooling the engine during its operation, in contrast to the prior art where coolers were only employed once an engine temperature threshold was exceeded. By providing constant cooling through the first coolant circuit, air is not allowed to build up in the circuit. The second engine outlet, which is valved by a thermostat, is connected to a second coolant circuit. The second coolant circuit is comprised of one or more of the left cooler, right cooler, rear cooler, and front cooler. Under this configuration, the second cooling circuit provides additional cooling capacity when the engine threshold temperature is exceeded.